U.S. patent application number 16/179387 was filed with the patent office on 2019-05-02 for press hardened steel with tailored properties.
The applicant listed for this patent is AK Steel Properties, Inc.. Invention is credited to Erik James Pavlina, Stephen Bryant Tate.
Application Number | 20190126400 16/179387 |
Document ID | / |
Family ID | 65041834 |
Filed Date | 2019-05-02 |
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United States Patent
Application |
20190126400 |
Kind Code |
A1 |
Pavlina; Erik James ; et
al. |
May 2, 2019 |
PRESS HARDENED STEEL WITH TAILORED PROPERTIES
Abstract
A tailor-welded blank is made of two steels, one steel of Alloy
A and one steel of Alloy B. Alloy A comprises 0.10-0.50 wt % C,
0.1-0.5 wt % Si, 2.0-8.0 wt % Mn, 0.0-6.0 wt % Cr, 0.0-2.0 wt % Mo,
0.0-0.15 wt % Ti, and 0.0-0.005 wt % B and wherein Alloy B
comprises 0.06-0.12 wt % C, 0.1-0.25 wt % Si, 1.65-2.42 wt % Mn,
0.0-0.70 wt % Cr, 0.08-0.40 wt % Mo, 0.0-0.05 wt % V, and 0.01-0.05
wt % Ti.
Inventors: |
Pavlina; Erik James;
(Lebanon, OH) ; Tate; Stephen Bryant; (Midland,
NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AK Steel Properties, Inc. |
West Chester |
OH |
US |
|
|
Family ID: |
65041834 |
Appl. No.: |
16/179387 |
Filed: |
November 2, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62580591 |
Nov 2, 2017 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B21D 22/022 20130101;
B21D 35/006 20130101; B23K 2101/185 20180801; C22C 38/02 20130101;
C22C 38/24 20130101; C22C 38/04 20130101; C21D 6/005 20130101; C22C
38/38 20130101; C21D 1/673 20130101; C21D 6/002 20130101; C23C 2/06
20130101; C23C 2/28 20130101; B23K 26/322 20130101; C22C 38/26
20130101; C23C 2/12 20130101; B23K 35/3086 20130101; C22C 38/32
20130101; C21D 1/22 20130101; C21D 1/19 20130101; B23K 35/3073
20130101; B23K 2101/34 20180801; C21D 6/008 20130101; C22C 38/12
20130101; C22C 38/14 20130101; C22C 38/22 20130101; C22C 38/28
20130101; B23K 2103/04 20180801; C21D 9/46 20130101 |
International
Class: |
B23K 26/322 20060101
B23K026/322; B23K 35/30 20060101 B23K035/30; C22C 38/04 20060101
C22C038/04; C22C 38/32 20060101 C22C038/32; C22C 38/38 20060101
C22C038/38; C22C 38/22 20060101 C22C038/22; C22C 38/26 20060101
C22C038/26; C22C 38/28 20060101 C22C038/28; C22C 38/24 20060101
C22C038/24; C22C 38/02 20060101 C22C038/02; C21D 6/00 20060101
C21D006/00 |
Claims
1. A tailor-welded blank comprising Alloy A and Alloy B, wherein
Alloy A comprises 0.10-0.50 wt % C, 0.1-0.5 wt % Si, 2.0-8.0 wt %
Mn, 0.0-6.0 wt % Cr, 0.0-2 wt % Mo, 0.0-0.1 wt % Nb, 0.0-0.1 Nb,
and 0.0-0.005 wt % B, the balance Fe and impurities associated with
steelmaking and wherein Alloy B comprises 0.06-0.12 wt % C,
0.1-0.25 wt % Si, 1.65-2.45 wt % Mn, 0.0-0.70 wt % Cr, 0.08-0.40 wt
% Mo, 0.0-0.1 Nb, 0.0-0.05 wt % V, 0.01-0.05 wt % Ti, and 0.0-0.002
wt % B, the balance Fe and impurities associated with
steelmaking.
2. The tailor-welded blank in accordance with claim 1, wherein the
carbon concentration in Alloy A is 0.1-0.35 weight %.
3. The tailor-welded blank in accordance with claim 2 wherein the
carbon concentration in Alloy A is 0.22-0.25 weight %.
4. The tailor-welded blank of claim 1, wherein the manganese
concentration in Alloy A is 2.0-5.0 weight %.
5. The tailor-welded blank of claim 1, wherein the manganese
concentration in Alloy A is 3.0 weight %-8.0 weight %.
6. The tailor-welded blank of claim 5; wherein the manganese
concentration in Alloy A is 3.0 weight %-5.0 weight %.
7. The tailor-welded-blank of claim 1, wherein the silicon
concentration in Alloy A is 0.2-0.3 weight %.
8. The tailor-welded blank of claim 1, wherein the molybdenum
concentration in Alloy A is 0.0-0.6 weight %.
9. The tailor-welded blank of claim 1, wherein the molybdenum
concentration in Alloy A is 0.1-2.0 weight %.
10. The tailor-welded blank of claim 9, wherein the molybdenum
concentration in Alloy A is 0.1-0.6 weight %.
11. The tailor-welded blank of claim 10, wherein the molybdenum
concentration in Alloy A is 0.4-0.5 weight %.
12. The tailor-welded blank of claim 1, wherein the chromium
concentration in Alloy A is 2.0-6.0 weight %.
13. The tailor-welded blank of claim 1, wherein the chromium
concentration in Alloy A is 0.2-6.0 weight %.
14. The tailor-welded blank of claim 13, wherein the chromium
concentration in Alloy A is 0.2-3.0 weight %.
15. The tailor-welded blank of claim 1, wherein the niobium
concentration in Alloy A is 0.01-0.1 weight %.
16. The tailor-welded blank of claim 15, wherein the niobium
concentration in Alloy A is 0.001-0.055 weight %.
17. The tailor-welded blank of claim 1, wherein the vanadium
concentration is 0.01-0.15 weight %.
18. The tailor-welded blank of claim 1, wherein Alloy A is coated
with aluminum, zinc, or alloys thereof.
19. The tailor-welded blank of claim 1, wherein Alloy B is coated
with aluminum, zinc, or alloys thereof.
20. A method of manufacturing a tailor-welded blank according to
claim 1 comprising the steps of: a. obtaining a steel of Alloy A,
b. obtaining a steel of Alloy B, c. welding the steel of Alloy A to
the steel of Alloy B; d. heating the welded blank to a temperature
above the Ac1 temperature for Alloy A, e. forming in a die, f.
cooling said blank in the die.
21. A method of manufacturing a tailor-welded blank according to
claim 1 comprising the steps of: a. obtaining a steel of Alloy A;
b. obtaining a steel of Alloy B; c. welding the steel of Alloy A to
the steel of Alloy B; d. heating the welded blank to a temperature
above the Ac3 temperature for Alloy A, e. forming in a die, f.
cooling said blank in the die.
Description
[0001] This application claims priority to U.S. Provisional Patent
Application No. 62/580,591 entitled "Press Hardened Steel with
Tailored Properties," filed on Nov. 2, 2017, the disclosure of
which is incorporated by reference herein.
BACKGROUND
[0002] Press hardened steels are produced via a hot stamping
process in which the steel is deformed at high temperatures at
which austenite is stable and then quenched in the stamping die at
sufficient cooling rates such that martensite is formed. These
steels are typically used in structural members in automotive
applications where high strength and high intrusion resistance are
required. Press hardened steels with tailored properties are
attractive for such applications because they can provide both high
intrusion resistance in addition to high energy absorption as the
result of relatively hard and soft areas in the component. Tailored
properties may be obtained through the use of tailor-welded blanks,
which are blanks composed of two steel sheets with different
compositions or thicknesses.
[0003] Typical commercial press hardened steels (for example,
22MnB5) have ultimate tensile strengths of approximately 1500 MPa
with total elongations of approximately 6-8%. Conventional press
hardened steel sheets may be joined to a steel with lower
hardenability, and which transforms to a softer microstructure
(ultimate tensile strengths of approximately 700 MPa) after press
hardening. This combination of steel is typically called a
tailor-welded blank (TWB). Press hardened TWBs result in components
that have tailored properties with regions of high strength and
relatively low elongation in areas that require intrusion
resistance and regions of lower strength and higher elongation in
areas that require energy absorption.
SUMMARY
[0004] The present compositions can be used in press hardened
steels, hot press forming steels, hot stamping steels, or any other
steel that is heated to an austenitizing temperature, formed, and
then quenched in a stamping die to achieve the desired final
properties of the stamped component. The current application
describes tailor-welded blanks composed of a high alloy steel that
can exhibit very high strengths after press hardening--up to 2,000
MPa--and a lower alloyed steel that can exhibit more moderate
strengths--up to 1,000 MPa--and higher elongation--up to 20%.
BRIEF DESCRIPTION OF THE DRAWING
[0005] FIG. 1 shows the ultimate tensile strength of steels
conforming to Alloy A and Alloy B after press hardening
simulations.
[0006] FIG. 2 shows the total elongation of steels conforming to
Alloy A and Alloy B after press hardening simulations.
DETAILED DESCRIPTION
[0007] A tailor-welded blank comprises a higher alloyed steel
(Alloy A) and a lower alloyed steel (Alloy B). After press
hardening, Alloy A forms a microstructure that exhibits higher
strength compared to Alloy B. In some embodiments, under some press
hardening conditions, the total elongation of Alloy A may exceed
that of Alloy B after press hardening.
[0008] Alloy A and Alloy B can each be made using conventional
steel making, roughing, and finishing processes. Embodiments of
Alloy A and Alloy B may each be bare or coated. Embodiments of
Alloy A and Alloy B can be joined by laser welding, or other known
joining techniques, to form a tailor-welded blank. During press
hardening, the TWB is heated to temperatures above the lower
critical temperature (Ac.sub.1) of Alloy A, transferred to a die,
formed, and then cooled in the die to achieve the desired final
properties. The Ac.sub.1 temperature for a given steel composition
is the temperature which corresponds to the boundary between the
ferrite+cementite phase field and the phase fields of
austenite+ferrite or austenite+cementite. The Ac.sub.1 temperature
for each composition of Alloy A can be determined by calculations
known in the art, or empirically, for example by dilatometry.
Calculations known in the art include the following three exemplary
calculations:
Ac.sub.1=723-10.7X.sub.Mn-16.9X.sub.Ni+29.1X.sub.Si+16.9X.sub.Cr+290X.su-
b.As+6.38X.sub.W.sup.1 Eqtn 1:
Ac.sub.1=739-22.8X.sub.C-60.8X.sub.Mn-15X.sub.Ni+18.2X.sub.Si+11.7X.sub.-
Cr+6.4X.sub.Mo+5X.sub.V-28X.sub.Cu.sup.2 Eqtn 2:
Ac.sub.1=754.83-32.25X.sub.C-17.76X.sub.Mn+23.32X.sub.Si+17.3X.sub.Cr+4.-
51X.sub.Mo+15.62X.sub.V.sup.3 Eqtn 3:
.sup.1K. W. Andrews, Empirical Formulae for the Calculation of Some
Transformation Temperatures, JISI, Vol. 203, 1965, pp.
721-727..sup.2 TRZASKA, J. et al. Modelling of CCT Diagrams for
Engineering and Constructional Steels. Journal of Materials
Processing Technology, 192-193, 2007, 504-510..sup.3KARIYA, N. High
Carbon Hot-Rolled Steel Sheet and Method for Production Thereof.
European patent Application EP 2.103.697.A1, 23.09.2009, 15 p.
[0009] Additionally, during press hardening, the TWB may also be
heated to temperatures above the upper critical temperature
(Ac.sub.3) of Alloy A, transferred to a die, formed, and then
cooled in the die to achieve the desired final properties. The
Ac.sub.3 temperature for a given steel composition is the
temperature which corresponds to the boundary between the
ferrite+austenite phase field and the austenite phase field. The
Ac.sub.3 temperature for each composition of Alloy A can be
determined by calculations known in the art, or empirically, for
example by dilatometry. Calculations known in the art include the
following exemplary calculation:
Ac.sub.3=910-203 {square root over
(X.sub.c)}-15.2X.sub.Ni+44.7X.sub.Si+104X.sub.V+31.5X.sub.Mo+13.1X.sub.W.-
sup.4 Eqtn 4:
.sup.4K. W. Andrews, Empirical Formulae for the Calculation of Some
Transformation Temperatures, JISI, Vol. 203, 1965, pp. 721-727.
[0010] Alloy A employs a novel alloying strategy that uses
substitutional elements to increase the strength of martensite
through a combination of substitutional solute strengthening and a
reduction in softening that results from autotempering. Softening
as a result of autotempering is minimized by suppression of the
martensite start temperature through alloying. As a result of the
increased hardenability in the proposed compositions that results
from various additions of manganese, chromium, molybdenum, and
niobium, the novel compositions permit a substantially boron-free
press hardening steel.
[0011] Alloy B employs an alloying strategy such that the
intercritical temperature of this alloy may overlap with that of
the higher alloyed Alloy A or overlap temperatures corresponding to
full austenitization of Alloy A. As a result, after press
hardening, the microstructure of Alloy B is primarily a mixture of
ferrite, bainite, and martensite.
[0012] Carbon is added to reduce the martensite start temperature,
provide solid solution strengthening, and to increase the
hardenability of the steel. Carbon is an austenite stabilizer. In
certain embodiments of Alloy A, carbon can be present in
concentrations of 0.1-0.50 weight %; in other embodiments, carbon
can be present in concentrations of 0.1-0.35 weight %; and in still
other embodiments, carbon can be present in concentrations of about
0.22-0.25 weight %. In certain embodiments of Alloy B, carbon can
be present in concentrations of 0.06-0.12 weight %; in other
embodiments, carbon can be present in concentrations of 0.08-0.1
weight %; in other embodiments, carbon can be present in
concentrations of 0.09-0.12 weight %; and in still other
embodiments, carbon can be present in concentrations of 0.06-0.085
weight %.
[0013] Manganese is added to reduce the martensite start
temperature, provide solid solution strengthening, and to increase
the hardenability of the steel. Manganese is an austenite
stabilizer. In certain embodiments of Alloy A, manganese can be
present in concentrations of 2.0-8.0 weight %; in other
embodiments, manganese can be present in concentrations of 2.0-5.0
weight %; in still other embodiments, manganese can be present in
concentrations of 3.0 weight %-8.0 weight %; and in still other
embodiments, manganese can be present in concentrations of greater
than 3.0 weight %-5.0 weight %. In certain embodiments of Alloy B,
manganese can be present in concentrations of 1.65-2.45 weight %;
in other embodiments, manganese can be present in concentrations of
2.2-2.45 weight %; in other embodiments, manganese can be present
in concentrations of 1.70-1.95 weight %, and in still other
embodiments, manganese can be present in concentrations of
1.65-1.85 weight %.
[0014] Silicon is added to provide solid solution strengthening.
Silicon is a ferrite stabilizer. In certain embodiments of Alloy A,
silicon can be present in concentrations of 0.1-0.5 weight %; in
other embodiments, silicon can be present in concentrations of
0.2-0.3 weight %. In certain embodiments of Alloy B, silicon can be
present in concentrations of 0.1-0.25 weight %; in other
embodiments, silicon can be present in concentrations of 0.1-0.2
weight %; and in other embodiments, silicon can be present in
concentrations of 0.15-0.25 weight %.
[0015] Molybdenum is added to provide solid solution strengthening,
to increase the hardenability of the steel, to provide
microstructural refinement, and to protect against embrittlement.
In certain embodiments of Alloy A, molybdenum can be present in
concentrations of 0-2.0 weight %; in other embodiments, molybdenum
can be present in concentrations of 0.0-0.6 weight %; in still
other embodiments, molybdenum can be present in concentrations of
0.1-2.0 weight %; in other embodiments, molybdenum can be present
in concentrations of 0.1-0.6 weight %; and in yet other
embodiments, molybdenum can be present in concentrations of 0.4-0.5
weight %. In certain embodiments of Alloy B, molybdenum can be
present in concentrations of 0.08-0.4 weight %; in other
embodiments, molybdenum can be present in concentrations of
0.08-0.15 weight %; in other embodiments, molybdenum can be present
in concentrations of 0.12-0.24 weight %; and in still other
embodiments, molybdenum can be present in concentrations of
0.14-0.25 weight %.
[0016] Chromium can be added to reduce the martensite start
temperature, provide solid solution strengthening, and increase the
hardenability of the steel. Chromium is a ferrite stabilizer. In
certain embodiments of Alloy A, chromium can be present in
concentrations of 0-6.0 weight %; in other embodiments, chromium
can be present in concentrations of 2.0-6.0 weight %; in other
embodiments, chromium can be present in concentrations of 0.2-6.0
weight %; and in other embodiments chromium can be present in
concentrations of 0.2-3.0 weight %. In certain embodiments of Alloy
B, chromium can be present in concentrations of 0.0-0.7 weight %;
in other embodiments, chromium can be present in concentrations of
0.5-0.7 weight %; in other embodiments, chromium can be present in
concentrations of 0.15-0.35 weight %; and in still other
embodiments, chromium can be present in concentrations of 0-0.1
weight %.
[0017] Niobium can be added to increase strength and improve
hardenability of the steel. In some embodiments niobium can also be
added to provide improved grain refinement. In certain embodiments
of Alloys A and B, niobium can be present in concentrations of
0-0.1 weight %; in other embodiments, niobium can be present in
concentrations of 0.01-0.1 weight %; and in other embodiments,
niobium can be present in concentrations of 0.001-0.055 weight %.
In certain embodiments of Alloy B, niobium can be present in
concentrations of 0.0-0.1 weight %; in other embodiments, niobium
can be present in concentrations of 0.03-0.05 weight %; in other
embodiments, niobium can be present in concentrations of
0.025-0.055 weight %; and in still other embodiments, niobium can
be present in concentrations 0.0-0.01 weight %.
[0018] Vanadium can be added to increase strength and improve
hardenability of the steel. In certain embodiments of Alloy A,
vanadium can be present in concentrations of 0-0.15 weight %; and
in other embodiments, vanadium can be present in concentrations of
0.01-0.15 weight %. In certain embodiments of Alloy B, vanadium can
be present in concentrations of 0.0-0.05 weight %; in other
embodiments, vanadium can be present in concentrations of 0-0.01
weight %; and in other embodiments, vanadium can be present in
concentrations of 0.02-0.05 weight %.
[0019] Boron can be added to increase the hardenability of the
steel. In certain embodiments of Alloy A, boron can be present in
concentrations of 0-0.005 weight %. In certain embodiments of Alloy
B, boron can be present in concentrations of 0.0-0.002 weight
%.
[0020] Titanium can be added increase the strength of the steel, to
control austenite grain size, and to control free nitrogen. In
certain embodiments of Alloy B, titanium can be present in
concentrations of 0.01-0.05 weight %; in other embodiments titanium
can be present in concentrations of 0.018-0.032 weight %; and in
other embodiments, titanium can be present in concentrations of
0.01-0.025 weight %.
[0021] The press hardened steels can be processed using
conventional steel making, roughing, and finishing processes. For
example, the steels of Alloy A and of Alloy B may each be
continuously cast to produce slabs approximately 12-25 cm in
thickness. Slabs may then be reheated at temperatures of
1200-1320.degree. C., and hot rolled to a final gauge of
.gtoreq.2.5 mm, with the final reduction pass occurring at a
temperature of approximately 950.degree. C. Steels may then be
coiled at temperatures of 400-675.degree. C. After cooling, the
steel coils may be annealed at temperatures of 600-900.degree. C.
for times longer than 1 second, and pickled, prior to cold
reduction. One or more intermediate annealing and reduction steps
may be required before reaching the desired thickness. Such
intermediate annealing utilizes temperatures similar to the first
annealing treatment.
[0022] The alloys of the present application can also be coated
with an aluminum-based coating, a zinc-based coating (either
galvanized or galvannealed), after cold rolling and before hot
stamping. Such coating can be applied to the steel sheet using
processes known in the art, including hot dip coating or
electrolytic coating. Because of the lower critical temperatures,
press hardening of the present alloys after they have been coated
is less likely to result in melting of the coating and the
detrimental effects associated with such melting.
[0023] In embodiments of the present invention, steel blanks of a
chosen Alloy A and chosen Alloy B are welded together to form a
TWB, they are then heated to a temperature above Ac1 for Alloy A,
transferred to a die, stamped, and cooled in accordance with
standard hot-stamping procedures. In other embodiments of the
present invention, steel blanks of a chosen Alloy A and chosen
Alloy B are welded together to form a TWB, they are then heated to
a temperature above Ac3 for Alloy A, transferred to a die, stamped,
and cooled in accordance with standard hot-stamping procedures.
Ultimate tensile strengths of approximately 2,000 MPa may be
achieved in Alloy A under appropriate press hardening conditions.
Under these same conditions, steels of Alloy B may result in
ultimate tensile strengths of approximately 700-980 MPa and total
elongations of 13-20%.
Example 1
[0024] Three steels, Alloy A-1, Alloy B-1, and Alloy B-2 were
prepared with the following nominal compositions in weight percent:
Alloy A-1 is 0.22% C, 5% Mn, 0.25% Si, 0.2% Cr,
Fe/impurities--balance; Alloy B-1 is 0.09% C, 2.3% Mn, 0.15% Si,
0.02% Ti, Fe/impurities--balance; and Alloy B-2 is 0.08% C, 1.7%
Mn, 0.18% Si, 0.013% Ti, 0.035% V, 0.017% Mo,
Fe/impurities--balance. The Ac.sub.1 temperature of Alloy A-1 is
approximately 677.degree. C. and was determined using
dilatometry.
[0025] Each of the steels were melted, cast, hot rolled, and cold
rolled in accordance with standard practice for stainless
steels.
[0026] Samples of each of the steels were heated to the peak metal
temperatures shown in FIGS. 1 and 2, and held for 300 s before
quenching in water-cooled dies. FIG. 1 shows the ultimate tensile
strength of steels conforming to Alloy A and B after press
hardening simulations. FIG. 2 shows the total elongation of steels
conforming to Alloy A and B after press hardening simulations.
[0027] FIGS. 1 and 2 show properties after simulated press
hardening of steels corresponding to the compositions of Alloy A
and B. Table 1 summarizes the properties after simulated press
hardening.
TABLE-US-00001 TABLE 1 Mechanical Properties of Alloys A and B
after Simulated Press Hardening Ultimate Peak Metal Yield Tensile
Uniform Total Temperature Strength Strength Elongation Elongation
Alloy (.degree. C.) (MPa) (MPa) (%) (%) A-1 700 892 954 10.9 16.1
A-1 700 926 971 10.0 14.6 A-1 700 848 983 13.7 18 A-1 700 840 976
13.1 16 A-1 715 536 1247 11.1 12.1 A-1 715 540 1248 10.6 11.1 A-1
715 637 1438 8.4 8.5 A-1 715 651 1457 8.1 8.2 A-1 725 668 1429 8.3
8.7 A-1 725 637 1412 8.1 8.1 A-1 725 970 1708 6.3 6.3 A-1 725 898
1664 7.0 7.3 A-1 710 479 1319 12.3 12.5 A-1 710 549 1387 10.2 10.5
A-1 710 583 1432 10.7 10.8 A-1 710 678 1515 7.3 7.3 A-1 710 649
1501 8.0 8.0 A-1 710 673 1549 7.5 7.5 A-1 745 1228 1871 6.2 8.2 A-1
745 1289 1869 4.7 6.7 A-1 745 1229 1858 5.4 7.4 A-1 745 1233 1843
5.9 7.9 A-1 745 1325 1895 5.3 7.2 A-1 745 1186 1831 5.1 7.4 A-1 759
1307 1995 5.9 7.4 A-1 759 1349 2027 6.4 8.2 B-1 680 682 713 10.9
14.8 B-1 680 688 707 10.8 15.1 B-1 695 584 628 16.4 24.0 B-1 695
574 622 16.6 25.7 B-1 710 541 630 17.3 24.6 B-1 710 551 629 17.9
25.6 B-1 725 366 682 15.7 20.4 B-1 725 390 716 15.9 21.5 B-1 740
405 852 12.7 16.4 B-1 740 406 858 12.1 15.4 B-1 755 491 983 9.6
13.0 B-1 755 491 984 10.1 13.5 B-1 775 623 1084 9.0 13.5 B-1 775
618 1075 8.9 13.1 B-2 680 559 609 12.4 19.2 B-2 680 581 624 12.5
17.5 B-2 695 482 542 18.3 26.9 B-2 695 493 539 18.4 28.8 B-2 710
464 524 19.1 30.1 B-2 710 459 524 19.9 29.0 B-2 725 424 519 20.7
28.2 B-2 725 424 519 21.5 30.8 B-2 740 276 600 16.0 21.6 B-2 740
267 590 16.8 22.7 B-2 755 321 695 15.2 20.2 B-2 755 320 693 14.8
20.6 B-2 775 350 743 14.3 19.9 B-2 775 353 754 13.7 19.8
Example 2
[0028] A tailor-welded blank is made of a steel of Alloy A welded
to a steel of Alloy B, wherein Alloy A and Alloy B contain the
compositions set forth in Table 2 below (wherein the balance of the
composition for each alloy is Fe and impurities associated with
steelmaking):
TABLE-US-00002 TABLE 2 Chemical Composition (in weight percent) of
Alloys A and B Alloy C Si Mn Cr Mo Nb V Ti B A 0.10-0.50 0.1-0.5
2.0-8.0 0.00-6.0 .sup. 0-2.0 0-0.1 0-0.15 -- 0-0.005 B 0.06-0.12
0.1-0.25 1.65-2.45 0-0.70 0.08-0.40 0-0.1 0-0.05 0.01-0.05
0-0.002
[0029] Process A: After welding, the blank is heated to a
temperature above the Ac1 temperature for Alloy A, transferred to a
die, formed, and then cooled in the die.
[0030] Process B: After welding, the blank is heated to a
temperature above the Ac3 temperature for Alloy A, transferred to a
die, formed, and then cooled in the die.
Example 3
[0031] A tailor-welded blank in accordance with the tailor-welded
blank of Example 2, or any or more of the following example,
wherein the carbon concentration in Alloy A is 0.1-0.35 weight %,
and alternatively 0.22-0.25 weigh %.
Example 4
[0032] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-3, or any or more of the
following examples, wherein the carbon concentration in Alloy B is
0.08-0.1 weight %; alternatively 0.09-0.12 weight %, or
alternatively 0.06-0.085 weight %.
Example 5
[0033] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-4, or any or more of the
following examples, wherein the manganese concentration in Alloy A
is 2.0-5.0 weight %; alternatively, 3.0 weight %-8.0 weight %; or
alternatively 3.0 weight %-5.0 weight %.
Example 6
[0034] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-5, or any or more of the
following examples, wherein the manganese concentration in Alloy B
is 2.2-2.45 weight %, alternatively 1.70-1.95 weight %, or
alternatively 1.65-1.85 weight %.
Example 7
[0035] A tailor-welded-blank in accordance with the tailor-welded
blank of any one or more of Examples 2-6, or any one or more of the
following examples, wherein the silicon concentration in Alloy A is
0.2-0.3 weight %.
Example 8
[0036] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-7, or any one or more of the
following examples, wherein the silicon concentration in Alloy B is
0.1-0.2 weight %, or alternatively 0.15-0.25 weight %.
Example 9
[0037] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-8, or any one or more of the
following examples, wherein the molybdenum concentration in Alloy A
is 0.0-0.6 weight %; alternatively, 0.1-2.0 weight %;
alternatively, 0.1-0.6 weight %; or alternatively 0.4-0.5 weight
%.
Example 10
[0038] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-9, or any one or more of the
following examples, wherein the molybdenum concentration in Alloy B
is 0.08-0.15 weight %, alternatively 0.12-0.24 weight %, or
alternatively 0.14-0.25 weight %.
Example 11
[0039] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-10, or any one or more of
the following examples, wherein the chromium concentration is
2.0-6.0 weight %; alternatively, 0.2-6.0 weight %; or alternatively
0.2-3.0 weight %.
Example 12
[0040] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-11, or any one or more of
the following examples, wherein the chromium concentration in Alloy
B is 0.5-0.7 weight %, alternatively 0.15-0.35 weight %, or
alternatively 0-0.1 weight %.
Example 13
[0041] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-12, or any one or more of
the following examples, wherein the niobium concentration is
0.01-0.1 weight %; or alternatively 0.001-0.055 weight %.
Example 14
[0042] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-13, or any one or more of
the following examples, wherein the niobium concentration in Alloy
B is 0.03-0.05 weight %, alternatively 0.025-0.055 weight %, or
alternatively 0.0-0.01 weight %.
Example 15
[0043] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-14, or any one or more of
the following examples, wherein the vanadium concentration is
0.01-0.15 weight %.
Example 16
[0044] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-15, or any one or more of
the following examples, wherein the vanadium concentration in Alloy
B is 0.0-0.01 weight %, or alternatively 0.02-0.05 weight %.
Example 17
[0045] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-16, or any one or more of
the following examples, wherein the titanium concentration in Alloy
B is 0.018-0.032 weight %, or alternatively 0.01-0.025 weight
%.
Example 19
[0046] A tailor-welded blank in accordance with the tailor-welded
blank of any one or more of Examples 2-17, or the following
example, wherein Alloy A is coated with aluminum or zinc, or alloys
thereof.
Example 20
[0047] A tailor-welded blank in accordance with the tailor-welded
blank of any or more of one of the Examples 2-19, wherein Alloy B
is coated with aluminum or zinc, or alloys thereof.
* * * * *